Abstract Biological nitrogen fixation (BNF) potential
of 12 soybean genotypes was evaluated in
conditions of low and sufficient phosphorus (P)
supply in two acid soils of southern Cameroon. The
P sources were phosphate rock (PR) and triple
superphosphate (TSP). The experiment was carried
out during two consecutive years (2001 and 2002) at
two locations with different soil types. Shoot dry
matter, nodule dry matter, and nitrogen (N) and P
uptake were assessed at flowering and the grain yield
at maturity. Shoot dry matter, nodule dry matter, N
and P uptake, and grain yield varied significantly
with site and genotypes (P\0.05). On Typic Kandiudult
soil, nodule dry matter ranged from 0.3 to
99.3 mg plant-1 and increased significantly with P
application (P\0.05). Total N uptake of soybean
ranged from 38.3 to 60.1 kg N ha-1 on Typic
Kandiudult and from 18 to 33 kg N ha-1 on Rhodic
Kandiudult soil. Under P-limiting conditions, BNF
ranged from -5.8 to 16 kg N ha-1 with significantly
higher values for genotype TGm 1511 irrespective of
soil type. Genotype TGm 1511 can be considered as
an important companion crop for the development of
smallholder agriculture in southern Cameroon.